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Martina, L.

Paper Title Page
THPCH152 Temporal Quantum Efficiency of a Micro-structured Cathode 3149
 
  • V. Nassisi, F. Belloni, G. Caretto, D. Doria, A. Lorusso, L. Martina, M.V. Siciliano
    INFN-Lecce, Lecce
 
  In this work the experimental and simulation results of photoemission studies for photoelectrons are presented*. The cathode used was a Zn disc having the emitting surface morphologically modified. Two different excimer lasers were employed like energy source to apply the photoelectron process: XeCl (308nm, 10ns) and KrF (248nm, 20ns). Experimental parameters were the laser fluence (up to 70 mJ/cm2) and the anode-cathode voltage (up to 20 kV). The output current was detected by a resistive shunt with the same value of the characteristic impedance of the sistem, about 100 ?. In this way, our device was able to record fast current signals. The best values of global quantum efficiency were approximately 5x 10-6 for XeCl and 1x 10-4 for KrF laser, while the peaks of the temporal quantum efficiency were 8x 10-6 and 1.4x10-4, respectively. The higher efficiency for KrF is ascribed to higher photon energy and to Schottky effect. Several electron-beam simulations using OPERA 3-D were carried out to analyze the influence of the geometrical characteristics of the diode. Simulating the photoemission by cathodes with micro-structures the output current was dependent on cathode roughness.

*L. Martina et al. Rev. Sci. Instrum., 73, 2552 (2002).